c-lightning: A specification compliant Lightning Network implementation in C
c-lightning is a standard compliant implementation of the Lightning Network protocol. The Lightning Network is a scalability solution for Bitcoin, enabling secure and instant transfer of funds between any two parties for any amount.
For more information about the Lightning Network please refer to http://lightning.network.
This implementation is still very much a work in progress. It can be used for testing, but it should not be used for real funds. We do our best to identify and fix problems, and implement missing features.
Any help testing the implementation, reporting bugs, or helping with outstanding issues is very welcome. Don't hesitate to reach out to us on IRC at #lightning-dev @ freenode.net, #c-lightning @ freenode.net, or on the implementation-specific mailing list email@example.com, or on the Lightning Network-wide mailing list firstname.lastname@example.org.
c-lightning currently only works on Linux (and possibly Mac OS with some
tweaking), and requires a locally (or remotely) running
bitcoind (version 0.15 or
above) that is fully caught up with the network you're testing on.
Pruning (prune=n option in bitcoin.conf) is not currently supported.
Please refer to the installation documentation for detailed instructions. For the impatient here's the gist of it for Ubuntu and Debian:
sudo apt-get update sudo apt-get install -y \ autoconf automake build-essential git libtool libgmp-dev \ libsqlite3-dev python python3 net-tools zlib1g-dev libsodium-dev git clone https://github.com/ElementsProject/lightning.git cd lightning ./configure make
Or if you like to throw
docker into the mix, you can use the official docker image either directly or as a base layer for more complex images.
The docker image is elementsproject/lightningd (from this Dockerfile).
Image tags with
-dev at the end are images built with
If you build the image yourself, you can use the build arg
DEVELOPER=1 to build c-lightning in developer mode.
It has the following environment variable:
EXPOSE_TCPdefault to false, if true, use expose c-lightning RPC on port 9835. (Use this only for testing)
Here is an example of a docker-compose file with bitcoind and c-lightning on
testnet which expose bitcoind's RPC interface on default ports
18332 and c-lightning API on port
version: "3" services: bitcoind: image: nicolasdorier/docker-bitcoin:0.16.3 container_name: bitcoind environment: BITCOIN_EXTRA_ARGS: | testnet=1 whitelist=0.0.0.0/0 server=1 rpcuser=rpcuser rpcpassword=rpcpass expose: - "18332" ports: - "0.0.0.0:18333:18333" volumes: - "bitcoin_datadir:/data" clightning_bitcoin: image: elementsproject/lightningd container_name: lightningd command: - --bitcoin-rpcconnect=bitcoind - --bitcoin-rpcuser=rpcuser - --bitcoin-rpcpassword=rpcpass - --network=testnet - --alias=myawesomenode - --log-level=debug environment: EXPOSE_TCP: "true" expose: - "9735" ports: - "0.0.0.0:9735:9735" volumes: - "clightning_bitcoin_datadir:/root/.lightning" - "bitcoin_datadir:/etc/bitcoin" links: - bitcoind volumes: bitcoin_datadir: clightning_bitcoin_datadir:
In order to start
lightningd you will need to have a local
node running in either testnet or regtest mode:
bitcoind -daemon -testnet
bitcoind has synchronized with the testnet network.
Make sure that you do not have
walletbroadcast=0 in your
~/.bitcoin/bitcoin.conf, or you may run into trouble.
Notice that currently pruned nodes are not supported and may result in
lightningd being unable to synchronize with the blockchain.
You can start
lightningd with the following command:
lightningd/lightningd --network=testnet --log-level=debug
Listing all commands:
cli/lightning-cli help will print a table of the API and lists the
Opening a channel on the Bitcoin testnet
First you need to transfer some funds to
lightningd so that it can
open a channel:
# Returns an address <address> cli/lightning-cli newaddr # Returns a transaction id <txid> bitcoin-cli -testnet sendtoaddress <address> <amount_in_bitcoins>
lightningd will register the funds once the transaction is confirmed.
You can obtain testcoins from a faucet such as coinfaucet.eu.
You can send them directly to the
You may need to generate a p2sh-segwit address if the faucet does not support bech32:
# Return a p2sh-segwit address cli/lightning-cli newaddr p2sh-segwit
lightningd got funds by:
# Returns an array of on-chain funds. cli/lightning-cli listfunds
lightningd has funds, we can connect to a node and open a channel.
Let's assume the remote node is accepting connections at
<port>, if not 9735) and has the node ID
cli/lightning-cli connect <node_id> <ip> [<port>] cli/lightning-cli fundchannel <node_id> <amount_in_satoshis>
This opens a connection and, on top of that connection, then opens
The funding transaction needs 1 confirmation in order for the channel
to be usable, and 6 to be broadcast for others to use.
You can check the status of the channel using
cli/lightning-cli listpeers, which after 3 confirmations (1 on testnet) should say
CHANNELD_NORMAL; after 6 confirmations you can use
cli/lightning-cli listchannels to verify that the
public field is now
lightning_openingdis negotiating channel opening.
lightning_channeldis waiting until the minimum number of confirmation on the channel funding transaction.
CHANNELD_NORMALmeans your channel is operating normally.
CHANNELD_SHUTTING_DOWNmeans one or both sides have asked to shut down the channel, and we're waiting for existing HTLCs to clear.
CLOSINGD_SIGEXCHANGEmeans we're trying to negotiate the fee for the mutual close transaction.
CLOSINGD_COMPLETEmeans we've broadcast our mutual close transaction (which spends the funding transaction) , but haven't seen it in a block yet.
FUNDING_SPEND_SEENmeans we've seen the funding transaction spent.
ONCHAINmeans that the
lightning_onchaindis tracking the onchain closing of the channel.
AWAITING_UNILATERALmeans that we're waiting for a unilateral close to hit the blockchain.
All these states have more information about what's going on in the
status field in
Sending and receiving payments
Payments in Lightning are invoice based.
The recipient creates an invoice with the expected
"any" for a donation), a unique
<label> and a
<description> the payer will see:
cli/lightning-cli invoice <amount> <label> <description>
This returns some internal details, and a standard invoice
bolt11 (named after the BOLT #11 lightning
The sender can feed this
bolt11 string to the
decodepay command to
see what it is, and pay it simply using the
cli/lightning-cli pay <bolt11>
Note that there are lower-level interfaces (and more options to these interfaces) for more sophisticated use.
lightningd can be configured either by passing options via the command line, or via a configuration file. Command line options will always override the values in the configuration file.
To use a configuration file, create a file named "config" within your ".lightning" directory. Usually, this will be ~/.lightning/config
Configuration options are set using a key=value pair on each line of the file, for example:
alias=SLEEPYDRAGON rgb=008000 network=testnet
For a full list of possible lightningd configuration options, run:
Developers wishing to contribute should start with the developer guide here.
JSON-RPC interface is documented in the following manual pages:
For simple access to the JSON-RPC interface you can use the
cli/lightning-cli tool, or the python API client.